Method and apparatus for scraping the inner walls of a vessel containing fluid

ABSTRACT

Method and apparatus for scraping the inner walls of a vessel containing fluid wherein the pressure exerted against said inner walls is controlled by regulating the weight of an actuating shaft of the scraping means.

United States Patent 1111 3,607,400

[72] Inventor Robert R. Goins [56] References Cited Bar 8- UNITED STATES PATENTS PP 8241447 9 9 1,469,896 10 1923 Cox 165 Flled Mal/124,1 1,949,374 2/1934 Johnson /94 x [451 patmed 111 2,011,032 8/1935 Blanchard... 165 94x Asslgnee plmilslemlelm 2,182,556 12 1939 Griswold..... 165 94 x 2,593,300 4/1952 Hachmuth... 23/273 x 2,615,793 10/1952 Weedrnan 23/273 2,617,273 11/1952 Findlay.... 23 273 x 2,626,856 1 1953 AlleS 23/285 x METHOD AND APPARATUS FOR SCRAPING THE 2,638,409 5/1953 BOtIal'O 196/1452 x INNERWALLSOFAVESSELCONTAININGFLUID 3,243,264 3/1966 Hickey .1 23/267.3x 3 Claims, 3 Drawing Figs.

Primary Examiner-Morrls O. Wolk [52] US. Cl 134/8, Assistant E i j h T Zamrga 23/267.3,23/273,23/285, 165/94, 196 145, and Quigg 208/37 51 1111.01 1308b 9 00 [50] Field of Search 134/6, 8, ABSTRACT: Method and apparatus for scraping the inner 22, 24, 169 R, 169 C; 210/; 208/37; 196/145, walls of a vessel containing fluid wherein the pressure exerted 14.52; 23/2673, 273 F, 285; l5/l04.05, 104.16; against said inner walls is controlled by regulating the weight 165/94, 95 of an actuating shaft of the scraping means.

METHOD AND APPARATUS FOR SCRAPING THE INNER WALLS OF A VESSEL CONTAINING FLUID This invention relates to a method and apparatus for scrap ing the inner walls of a vessel containing fluid. In another aspect, this invention relates to an improved scraped surface chiller.

This invention relates to a device for cleaning deposits from a heat transfer surface of a double-pipe heat exchanger, a scraped surface chiller, and the like. For example, in the separation of wax from petroleum fractions containing the same, it is customary to chill the petroleum fraction by pumping it through the interior pipe of a double-pipe heat exchanger. That is to say, the pipe through which the oil is pumped is surrounded by another pipe or jacket and a cooling material such as chilled brine is pumped through annular spaces between the two pipes. The oil in the interior pipe being chilled tends to form deposits upon the inside of the wall of the pipe through which it flows. These deposits not only slow down the rate of heat exchange through the pipe wall, but also the material which is deposited is wax which is desired to separate from the oil and must not be allowed to remain within the cooler. So it is customary to provide scraping devices of various kinds to remove this material from the wall of the pipe. A most usual and simple form of scraper for this purpose is the blade carried on and rotated by a central shaft.

Scraped surface chillers are used in a variety of applications for chilling many liquids, notably hydrocarbons, in order to precipitate out solid materials. In some cases, the chiller is used to cool the liquid and frees from it solid material which settles out readily at the colder temperature. In other cases, a scraped surface chiller is an element in a system for separating liquids by means of fractional crystallization. In the latter case, the liquids fed to the chiller are cooled to a temperature at which at least a portion of one component precipitates out as crystals. Thereafter, the crystal slurry is fed to crystal means.

F luid-containing vessels which periodically require scraping of the inner surface, are generally elongated and of sometimes great length. During scraping of these surfaces, it is often a problem to contact the entire inner surface of the vessel with equal force. This problem is principally caused by the actuating shaft and scraping equipment being heavy and having a density differing from that of the fluid within which the scraping action is being performed. The unequal force exerted against the inner surface of the vessel by the scraper is greatly exaggerated where the chamber of the vessel is generally parallel to the surface of the earth. In such a situation, an actuating shaft having a density greater than the fluid contained within the vessel will cause the scraper to apply a greater force downwardly against the bottom portion of the inner surface of the horizontal vessel. An actuating shaft having a density less than the fluid contained within the vessel will conversely apply a greater force against the upper portion of the vessel. In either event, the efficiency of the scraping process will be reduced and useful life of the scraper will be shortened.

It is therefore an object of this invention to provide an improved method and apparatus for scraping the inner walls of a vessel containing fluid. Another aspect of this invention is to provide an improved method and apparatus of the above type which will apply equal forces to the inner surface of the vessel. Yet another object of this invention is to provide an apparatus of the above type having an actuating shaft with an adjustable weight per unit length. Afurther object of this invention is to provide an apparatus of the above type which can be regulated to apply greater or lesser forces against the upper or lower inner surfaces of a horizontal vessel containing fluid. Other aspect, objects, and advantages of the present invention will become apparent from a study of the disclosure, the appended claims, and the drawing.

In the drawing, FIG. 1 is a diagrammatic sketch in partial longitudinal section of the scraping means and vessel being scraped. FIG. 2 is a diagrammatic sketch in partial longitudinal section of another embodiment of the actuating shaft of this invention. FIG. 3 is a diagrammatic sketch in partial longitudinal section of another embodiment of the actuating shaft of this invention.

Referring to FIG. 1, a vessel 2 containing fluid 4 has a longitudinal chamber 6 extending therethrough. A scraper 8 has scraper blades 10 in contact with a circumferential portion of the inner walls 12 of the vessel 2. An actuating shaft 14 having a longitudinal chamber extending therethrough and first and second end portions 18, 20 is attached at the first end portion to the scraper 8, extends through the chamber 6 of the vessel 2, passes through sealing means 22 mounted on the vessel and extends beyond said vessel. A port 24 is formed on an end of the vessel 2 in communication with the chamber 6. A valve means 26 is mounted on the actuating shaft 14 for sealing the chamber 16 of the actuating shaft 14 and providing a passage for material into and from said chamber 16. The actuating shaft 14 is rotatable and longitudinally movable relative to the vessel 2 for moving the scraper 8 over the inner walls 12 of the vessel. This invention can also be used with a conventional scraped surface chiller which does not require longitudinal movement of the scraper 8. The blades of the scraping means can be of any conventional configuration. The shaft 14 can also be constructed so that the weight of the shaft is substantially equal to or less than the weight of the fluid within the vessel 2 that is displaced by the shaft.

Referring to FIG. 2 which shows another embodiment of the actuating shaft 14 of this invention, a plurality of partitions 28 are rigidly attached to the inner walls 30 of the actuating shaft 14 for separating the chamber 16 of said actuating shaft into a plurality of individual, separate regulating compartments 32. Separate valve means 26 are associated with each regulating compartment 32 for the passing of fluid into and from said compartment.

Referring to FIG. 3 which shows yet another embodiment of the shaft 14 of this invention, a weight bar 34 having a controlled weight per unit length and centralizers 36 spaced longitudinally on said bar is positioned within the chambers 16 of the actuating shaft 14 with the centralizers in contact with the inner walls 30 of said shaft.

In the operation of this invention, the fluid 4 contained within the vessel 2 is measured to determine its density. Measurements are thereafter taken of the actuating shaft 14 to determine the volume of fluid displaced by the submergence of a unit length of the shaft within the fluid 4 and the dry weight of the unit length of the shaft. A volume of weighting liquid 38 is thereafter passed into the chamber 16 of the actuating shaft 14 via the valve means 26 to increase the weight of each unit length of the shaft within the vessel 2. After the weight of the actuating shaft 14 is increased to be equal to the weight of the displaced fluid 4, the weight of the shaft will no longer exert upwardly or downwardly directed forces through the scraper and against the inner walls 12 of the vessel 2.

Referring to FIG. 3, in situations where the scraper of this invention is utilized in a plurality of vessels containing differing fluids, but where each fluid maintains a constant density, a weight bar 34 can be utilized to adjust the weight per unit length of the actuating shaft 14. Here, measurements and calculations as described above will be made to determine the weight per unit length of the weight bar for each different fluid. A weight bar is then formed which has a specific weight per unit length and the bar is marked for use in the specific fluid and vessel for which it was constructed. Insertion of the correct weight bar, for scraping within the fluid of its respective vessel, permits the operator to effectively and efficiently scrape a plurality of vessels without repeatedly calculating the weight requirements needed.

In the operation of the embodiment of this invention shown in FIG. 2, weighting liquid 38 is placed not in one longitudinal chamber 16 within the actuating shaft 14, but separate individual volumes of said liquid is placed in separate regulating compartments 32. This embodiment of the invention permits the operator not only to regulate the weight of the actuating shaft 14 to a weightless condition within the fluid 4 of the ves- 5e12, but in addition allows the operator to selectively control the pressure exerted by the blades 10 on the inner walls 12 of the vessel 2.

The force exerted by buoyancy of the actuating shaft 14 can be regulated to exactly equal the weight of the scraper 8, thereby exactly maintaining equal forces exerted on the vessel by the blades 10. In situations where more vigorous scraping is desired on the lower portion of the vessel, more weighting liquid 38 can be added to the compartments 32 positioned on the first end portion 18 of the actuating shaft 14. Where it is desired to more vigorously scrape the upper portion of the vessel 2, less weighting liquid 38 is placed in the regulating compartments 32 located at the first end of the actuating shaft 14. Canting of the scraper 8 can be accomplished by adjusting the weighting liquid level within regulating compartments 32 positioned at other locations.

The desired canting and buoyancy above described can likewise be accomplished in the embodiment employing the weight bar by controlling and varying the weight per unit length of said weight bar.

By so controlling the weight of the actuating shaft 14 of the scraper means 8 of this invention, the walls 12 of the vessel 2 containing fluid 4 can be scraped with improved efficiency and control.

Other modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing discussion and accompanying drawings, and it should be understood that this invention is not to be unduly limited thereto.

That which is claimed is:

l. A method of scraping the inner surface of a vessel containing fluid comprising,

inserting a scraper blade and an actuating shaft having a longitudinal chamber therewithin into the vessel, the vessel being longitudinally disposed in other than a vertical aspect and the scraper blade being in contact with a circumferential portion of the inner wall of said vessel and connected to one end of the actuating shaft with the other end of the actuating shaft extending through an end of the longitudinal vessel,

passing fluid into said vessel,

passing a volume of weighting material into the chamber of the actuating shaft to vary the weight per unit length of the shaft to a weight substantially equal to the volume of fluid displaced by the submergence of each unit length of the shaft in the fluid within the vessel so as to provide substantial equal distribution of scraping forces about substantially the entire circumferential inner surface of the vessel contacted by the scraper blade during movement of said blade, and

moving the actuating shaft and connected scraper blade with the scraper blade in contact with the scraper blade in contact with said inner surface of said vessel.

2. A method as set forth in claim 1, wherein said material is a fluid passed into and from said longitudinal chamber of said actuating shaft.

3. A method as set forth in claim 1, wherein said material is a longitudinal weight bar inserted into said longitudinal chamber of said actuating shaft.

3 ,607 ,400 Patent No.

Dated September 21 1971 Inventor(s) Claim 1 column 4 line line Claim 2 column 4 line Claim 3, column 4 line (SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer Robert R. Goins It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

after "contact" delete "with the scraper blade in";

delete first word "contact".

after "said" and before "material" insert weighting after "said" and before "material" insert weighting Signed and sealed this 21st day of March 1972 ROBERT GOTTSCHALK Commissioner of Patents RM PO-IOSO (10-59) 

2. A method as set forth in claim 1, wherein said material is a fluid passed into and from said longitudinal chamber of said actuating shaft.
 3. A method as set forth in claim 1, wherein said material is a longitudinal weight bar inserted into said longitudinal chamber of said actuating shaft. 